u can use a nand schmitt trigger too...
X = ((HIGH NAND X) NAND HIGH)
F = ((T) NAND T)=F
T = ((F) NAND T)=T
a LDR sounds good too...
i still think that the arduino pin has something like a schmitt trigger builtin...
what does the scope say?
did u try that debounce library? i guess those blinks r 30msec long...
even if u tell the debounce library to skip 40msec, u could detect >10Hz...
after 160secs u could have 1kWh (max)...
that limits ur load to 22.5kW (22 vacuum cleaners)...
do u know this site:
http://www.bwired.nl/Stroom.asp
?
they use an IR sensor 2...